全文获取类型
收费全文 | 1821篇 |
免费 | 117篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 13篇 |
化学工业 | 424篇 |
金属工艺 | 37篇 |
机械仪表 | 30篇 |
建筑科学 | 72篇 |
矿业工程 | 2篇 |
能源动力 | 60篇 |
轻工业 | 152篇 |
水利工程 | 7篇 |
石油天然气 | 5篇 |
无线电 | 216篇 |
一般工业技术 | 369篇 |
冶金工业 | 112篇 |
原子能技术 | 23篇 |
自动化技术 | 417篇 |
出版年
2023年 | 21篇 |
2022年 | 34篇 |
2021年 | 37篇 |
2020年 | 52篇 |
2019年 | 51篇 |
2018年 | 56篇 |
2017年 | 67篇 |
2016年 | 67篇 |
2015年 | 55篇 |
2014年 | 65篇 |
2013年 | 133篇 |
2012年 | 117篇 |
2011年 | 155篇 |
2010年 | 103篇 |
2009年 | 100篇 |
2008年 | 111篇 |
2007年 | 89篇 |
2006年 | 88篇 |
2005年 | 73篇 |
2004年 | 58篇 |
2003年 | 48篇 |
2002年 | 39篇 |
2001年 | 18篇 |
2000年 | 17篇 |
1999年 | 29篇 |
1998年 | 31篇 |
1997年 | 43篇 |
1996年 | 27篇 |
1995年 | 17篇 |
1994年 | 20篇 |
1993年 | 19篇 |
1992年 | 12篇 |
1991年 | 8篇 |
1990年 | 9篇 |
1989年 | 8篇 |
1988年 | 8篇 |
1987年 | 4篇 |
1986年 | 5篇 |
1985年 | 6篇 |
1984年 | 6篇 |
1983年 | 5篇 |
1982年 | 7篇 |
1977年 | 5篇 |
1976年 | 5篇 |
1975年 | 3篇 |
1973年 | 1篇 |
1972年 | 1篇 |
1971年 | 1篇 |
1967年 | 1篇 |
1954年 | 1篇 |
排序方式: 共有1939条查询结果,搜索用时 140 毫秒
981.
Jean-Franois Coutouly Pascal Deprez Florin Breaban Jean-Paul Longuemard 《Journal of Materials Processing Technology》2009,209(17):5730-5735
The ablation of coatings (paint, varnish, oxides, etc.) using a pulsed laser beam is a process that has a number of major benefits compared with conventional cleaning techniques (mechanical and chemical), the main advantage being the possibility of removing the surface layer without any risk of damaging the substrate. Another benefit, and certainly not the least, is the non-use of toxic solvents or chemical products that are difficult to eliminate and, in any case, will be banned from use in the near future. However, it must be stressed that, notwithstanding the above benefits, laser ablation of painted surfaces can only give good quality results if the process is properly controlled. The procedure discussed in this paper has two aims: the first involves establishing a thermal model of the interaction, applied to the ablation of paint from metal surfaces by infra-red laser. The second involves proposing an optimised paint removal process validated by experimental measurements. This second objective will be based on an analysis method of the acoustic signal transmitted by the ablation plasma beam. 相似文献
982.
To develop high performance steels for automotive applications, enhanced strengthening mechanisms are required. This study aims at assessing the critical parameters leading to the refinement of the strain‐induced ferrite matrix of thermomechanically processed multiphase steels. Hot rolling simulations allowed the definition of the temperature, strain and cooling rate conditions bringing about the formation of strain‐induced ferrite with a reduced grain size. The relationship between the deformation and the concurrent or subsequent phase transformations is highlighted thanks to a thorough characterisation of the generated microstructures. It is also shown that the prior austenite grain size influences the distribution of the second phases within the finely grained ferrite matrix. 相似文献
983.
984.
OBJECTIVES: Compare the effect of high doses of inhaled corticosteroids on bone loss in subjects with moderate to severe asthma or mild asthma, and examine the influence of dietary intake on bone metabolism. DESIGN: A survey on the effects of corticotherapy and nutrition on bone density was conducted in 74 subjects currently being treated for asthma in the asthma clinic of H?pital Laval (Sainte-Foy, Quebec, Canada). Fifty-eight subjects completed the study (attrition rate = 15%). MAIN OUTCOME MEASURES: In all subjects expiratory volumes were determined and urinary analysis was conducted for hydroxyproline, calcium, phosphorus, and cortisol levels. Osteocalcin, calcium, phosphorus, cortisol, alkaline phosphatase, and gamma-glutamyltransferase levels were measured in blood samples. Bone density of the lumbar spine was determined by means of dual-energy x-ray absorptiometry. Nutrition evaluation was based on a 3-day food diary analyzed using progiciel Nutri 91. The nutritional parameters examined were calcium; phosphorus; magnesium; zinc; vitamins A, C, and D; protein; total fiber; oxalates; energy; caffeine; and alcohol in relation to bone density. SUBJECTS: Thirty-one patients with moderate to severe asthma who had been taking more than 1,000 micrograms beclomethasone per day or the equivalent for more than 2 years and 27 patients with mild asthma who were taking less than 500 micrograms beclomethasone per day or the equivalent. STATISTICAL ANALYSES PERFORMED: Four-factor analysis of variance with hierarchized interactions of four levels, Duncan's test, Pearson correlation coefficients. RESULTS: Blood levels of osteocalcin and protein intake were lower in patients with moderate to severe asthma than in those with mild asthma (P < .05). Significant correlations (P < .02) were observed between bone density and calcium intake (r = .40), phosphorus intake (r = .35), protein intake (r = .30), and serum alkaline phosphatase level (r = -.30). Bone density was not significantly different between the two groups of patients with asthma. APPLICATIONS: A follow-up of patients with asthma who are taking inhaled corticosteroids is needed to assess bone density, osteocalcin levels, and dietary intakes of calcium. Verify if osteocalcin level decreases over time in patients with moderate to severe asthma, monitor possible modifications in bone density, and verify if the correlation between dietary calcium and bone density is maintained. 相似文献
985.
Tim Van Rompaey Frederic Lani Bart Blanpain Patrick Wollants Pascal J. Jacques Thomas Pardoen 《Metallurgical and Materials Transactions A》2006,37(1):99-107
A three-dimensional finite-element microstructural cell model involving an inclusion of retained austenite embedded within
a ferrite grain, which is surrounded by a homogeneous matrix representing the behavior of a transformation-induced-plasticity
(TRIP)-assisted multiphase steel, was developed in order to address the micromechanics of the martensitic transformation in
small isolated austenite grains. The transformation of a single martensite plate is simulated after various amounts of prior
plastic deformation under different in-plane loading conditions. The values of the mechanical driving force and of the elastic
and plastic accommodation energies associated with the transformation are calculated as a function of the externally applied
loading conditions. The mechanical driving force and the total accommodation energy are of the same order of magnitude. The
mechanical driving force depends upon the stress state and is the highest for plane-strain conditions. The total accommodation
energy is almost independent of the stress state. It is affected by the amount of plastic straining prior to transformation
and is very much dependent on the level of the shear component of the transformation strain. The results of this study provide
guidelines for the development of realistic stress-state-dependent transformation evolution laws for TRIP-assisted multiphase
steels. 相似文献
986.
Daniel Beysens Marc Muselli Iryna Milimouk Catherine Ohayon Simon M. Berkowicz Emmanuel Soyeux Marina Mileta Pascal Ortega 《Energy》2006
Dew water was collected from several passive foil-based radiative condensers established in a variety of geographic settings: continental (Grenoble, in an alpine valley, and Brive-la-Gaillarde, in the Central Massif volcanic area, both in France), French Atlantic coast (Bordeaux), eastern Mediterranean (Jerusalem, Israel), and the island of Corsica (Ajaccio, France) in the Mediterranean Sea. In Ajaccio two large 30 m2 condensers have been operating since 2000. Additional semi-quantitative dew measurements were also carried out for Komi?a, island of Vis (Croatia) in the Adriatic Sea, and in Mediterranean Zadar and Dubrovnik (both in Croatia). Dew potential was calculated for the Pacific Ocean island of Tahiti (French Polynesia). The data show that significant amounts of dew water can be collected. Selected chemical and biological analyses established that dew is, in general, potable. Continued research is required for new and inexpensive materials that can enhance dew condensation. 相似文献
987.
Pascal Elleaume Anmick Ropert 《Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment》2003,500(1-3):18-24
Rings of 6–8 GeV with circumstance of about 2 km or more could provide X-ray brightness that significantly exceeds that of any present facility, opening new research opportunities. 相似文献
988.
This paper presents a performance analysis of optical burst switching (OBS) networks with ring and chordal ring topologies. The performance analysis considers signaling protocols with one-way reservation schemes, being focused on the following protocols: just-in-time (JIT), Jumpstart, JIT+, just-enough-time (JET) and Horizon. It is shown that for a network with 20 nodes, the nodal degree gain due to the increase of nodal degree from two (ring) to three (chordal ring) is about three orders of magnitude in the first hop of both topologies, and is between two and three orders of magnitude in the last hop of each topology. It is also shown that the largest chord length gain, in a 20-node OBS network with a chordal ring topology, is slightly less than two orders of magnitude. 相似文献
989.
Pascal Viville Philippe Leclère Michel Schappacher Redouane Borsali Roberto Lazzaroni 《Polymer》2004,45(6):1833-1843
This work deals with the study of comb-like vs. arborescent grafted copolymers made of poly(chloroethyl vinyl ether)-g-polystyrene (PCEVE-g-PS). We describe how the molecular architecture of the branched polymers affects their nanoscale organization in thin films, as observed using atomic force microscopy. The results indicate that modifying the molecular architecture from a ‘generation-zero’ comb-like (PCEVE-g-PS) to a ‘first-generation’ hyperbranched (PCEVE-g-(PS-b-PCEVE-g-PS)) architecture strongly modifies the observed geometrical parameters of the molecules, in good agreement with the expected evolution of the molecular dimensions and the corresponding data obtained in solution.The surface organization of the (PCEVE-g-PS) copolymer molecules is also strongly conditioned by the interplay between the molecule-substrate interactions and the molecule-molecule interactions, leading to different possible orientations of the lateral branches with respect to the surface and thus to different final morphologies. 相似文献
990.
Nanocrystalline Titanium Oxide Electrodes for Photovoltaic Applications 总被引:15,自引:0,他引:15
Christophe J. Barbé Francine Arendse Pascal Comte Marie Jirousek Frank Lenzmann Valery Shklover Michael Grätzel 《Journal of the American Ceramic Society》1997,80(12):3157-3171
During the past five years, we have developed in our laboratory a new type of solar cell that is based on a photoelectrochemical process. The light absorption is performed by a monolayer of dye (i.e., a Ruthenium complex) that is adsorbed chemically at the surface of a semiconductor (i.e., titanium oxide (TiO2 )). When excited by a photon, the dye has the ability to transfer an electron to the semiconductor. The electric field that is inside the material allows extraction of the electron, and the positive charge is transferred from the dye to a redox mediator that is present in solution. A respectable photovoltaic efficiency (i.e., 10%) is obtained by the use of mesoporous, nanostructured films of anatase particles. We will show how the TiO2 electrode microstructure influences the photovoltaic response of the cell. More specifically, we will focus on how processing parameters such as precursor chemistry, temperature for hydrothermal growth, binder addition, and sintering conditions influence the film porosity, pore-size distribution, light scattering, and electron percolation and consequently affect the solar-cell efficiency. 相似文献